1925 GMT: Former Formula 1 champion Damon Hill has expressed concern over the staging of the Bahrain Grand Prix, ""It would be a bad state of affairs, and bad for Formula One, to be seen to be enforcing martial law in order to hold the race. That is not what this sport should be about."

In February, Hill had appeared to support the staging of the race, "There are sincere efforts to resolve the difficulties. There has been a change. Human rights organisations say there is a process in place to help Bahrain recover its reputation."

However, Hill, who won the title in 1996, said today, "Things are different now. The protests have not abated and may even have become more determined and calculated. It is a worrying state of affairs."

1845 GMT: Over the past two days, we have raised questions about the current trip of four members of the US Congress to Bahrain, a visit used by the regime as a public-relations bonanza. Now one of the four legislators, Democrat Jim Himes, has posted messages on Twitter:

On way back from #Bahrain. Visited sailors, govt officials and opposition. Also toured villages where protestors are met with tear gas.